1. Field of the Invention
The present invention relates to a recording and/or reproducing apparatus for still images, such as those known as electronic still cameras and, more particularly, to electronic still cameras capable of recording an audio portion in association with the still image or scene.
2. Description of the Background
There are now known electronic still cameras that have in place of the conventional silver halide film a solid-state image pickup device, such as a charge coupled device, or CCD, for recording a still image or scene on a magnetic record disc. One example of such electronic still camera is found in British Patent Publication No. GB212603A. The still camera described in this British Patent Publication is designed so that one-field or one-frame of the video signal from the image pickup device is taken during the time that the shutter is opened, which means the signal corresponding to the one-frame is recorded on one complete annular track of a magnetic disc.
In the unit intended for reproducing the images recorded by such electronic still cameras, the video signal of the recorded still image or scene is formed by repeated reproduction of one track, or repeated alternate reproduction of two tracks in the format in which only a single field is recorded on each track, two fields making up a frame. Such reproduced video signals then are supplied to a television monitor or television receiver for reproducing the still images on the cathode ray tube screen. Additionally, a so-called video printer has also been proposed for printing a hard copy of the image recorded by the electronic still camera.
Further proposals that have been made relative to the electronic still camera involve a provision of recording ambient sounds or human voice narration associated with the still image or scene that is being recorded. A workable length for such audio material has been found to be approximately ten seconds. In recording such audio signals, the recording system used for the video signals may be used by compressing the audio signals along the time axis using, for example, digital signal processing, thereby elevating the bandwidth of the audio signals to that of the video signals. For example, using such time-base compression an audio signal having a bandwidth of 5kHz, can be compressed along the time axis by a factor of 600 to raise the bandwidth of the signals to the video signal bandwidth, such as 3MHz, so that audio signals can be recorded having a time duration of about ten seconds, which is about 600 times the duration of one field period which is typically equal to 1/60th of a second. This technique in theory works fine except that an extremely large capacity memory device is required if ten seconds worth of audio signals must be digitally processed in the manner as described above.
Accordingly, it has been proposed to divide the ten second period corresponding to the desired audio program length into four equal parts of 2.5 seconds duration each, and then to digitally process these individual parts in order to reduce the required memory capacity. Each of the quadrisectioned, time-axis compressed, continuous audio signals is sequentially and continuously recorded on each of the four sectors or segments obtained by dividing a given track on the magnetic disc into four equal sections. Nevertheless, while recording the series of video signals on the four segments of one track solves one problem, other problems are presented by this approach. For example, when the continuous audio signals are divided into a number of portions or segments, it becomes difficult to maintain signal continuities between the successive segments at the time of reproduction. Also, in similar situations when the audio signals are recorded in a plurality of successive tracks, in cases where the audio signals have a duration longer than ten seconds, it becomes difficult to maintain signal continuities between the successive tracks during reproduction. Also, when the audio signals are recorded for only two seconds, for example, on a track capable of recording audio signals of a ten second duration, the remaining eight second period will be void of signals, however, it is still necessary to perform the audio reproducing operation for the entire ten seconds of the track in order to reproduce only the two seconds of audio signals recorded thereon. Furthermore, because the audio signals associated with the next successive image or scene can be recorded only at intervals of ten seconds, it is not possible during continuous shooting to record the sound or voice associated with each scene of the continuous series. Similarly, when the audio signals are recorded over a plurality of tracks, it is difficult to distinguish the image track from the audio track so that the sound or voice is not always produced in association with the appropriate scene.